It is known in the art that an electromagnet can be powered by energizing the associated coil using a high level of current known as the trigger current to cause the movable magnetic circuit of the electromagnet to rise; the movable magnetic circuit can then be maintained using a low current known as the holding current. This minimizes consumption and heat dissipation.
In order for successive high and low currents to be used a coil may consist of two windings: a principal coil dimensioned to carry most of the trigger current and an auxiliary winding sufficiently dimensioned to supply the power required to retain the movable armature.
The large size of this type of double-winding coil, however, is a considerable drawback.
To overcome these problems coils exist in which a single winding is connected to single high-voltage source. Since the winding is dimensioned to carry the trigger current the power supply circuit is fitted with a chopper device that serves to lower the current energizing the coil to its holding level. However this type of device is costly and must be adapted to each voltage used, whether 100 V or 400 V.
It is therefore a purpose of the present invention to energize a single-winding electromagnet coil using a low-cost power supply circuit that can be used equally well at voltages ranging from 100 to 500 Volts.